Heterosis and Genetic Load Investigated in a Partial Diallel Cross

Hybrid vigor or heterosis, which is the increased performance of the hybrid progenies compared to their homozygous parents, reaches high levels in maize with certain combinations of complementary heterotic groups. Three main genetic mechanisms have been proposed to explain heterosis: dominance, overdominance and positive epistatic interactions.

In order to better understand these mechanisms, a partial diallel crossing scheme (reciprocals were bulked) was employed using 12 inbred lines, representative of the current U.S. commercial germplasm base. The 66 resulting hybrids were phenotyped along with their inbred parents, and the inbred parents were sequenced making it possible to directly link heterosis to genetic differences between inbred lines.

More than 12 million SNPs were identified with 99% accuracy. Characterization of deleterious mutations in the 12 inbred lines and association mapping results for heterosis and different quantitative traits will be presented and discussed.

Through this project, we aim to explore how a better understanding of the basis of heterosis can contribute to more accurate estimation of breeding values and prediction of performance for increased efficiency in genetic improvement of maize.